9781888569605-ch104

Benthic Habitats and the Effects of Fishing

Symposium Abstract: Ecological Footprints of Scotian Shelf Groundfish Fisheries

K. C. T. Zwanenburg, M. Showell, and S. Wilson

doi: https://doi.org/10.47886/9781888569605.ch104

We examine by-catch (non-directed catch) of commercial and non-commercial demersal fish species for a number of Scotian Shelf fisheries over the past two decades to determine their relative impacts. Although by-catch of commercial species is readily available (landings), by-catch of non-commercial species exists for only a small subset of fisheries. Landings data give conservative estimates of fishery impacts because they record only commercial species, while observing catches is costly but estimates non-commercial by-catch. We compare impacts of fisheries as derived from landings and on-board observer data. The impacts are cast as ecological footprints with the number of by-catch species defining breadth and the rates of by-catch defining depth of the footprints. From landings data, the proportions (by weight) caught as directed catch ranges from less than 1% (narrow footprints) to as high as 100% (broad footprints) while by-catch rates in these same fisheries range from near 0% (shallow footprints) to near 100% (deep footprints). True breadth and depth (in species space) of ecological footprints can; however, only be derived from observed catches. These are available for only a small subset of fisheries. The Atlantic halibut (Hippoglossus hippoglossus) fishery catches 40 additional species with 13 at a rate of 1% or more of the total halibut caught. These analyses provide a classificatory framework useful for allocating additional investigative efforts to particular fisheries with broad or deep footprints. Long-term impacts of by-catches can also be estimated by hindcasting the potential cumulative impacts of fisheries based on current by-catch profiles.